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USER’S GUIDE RS232 PC-FAX EXPANDER Type 185
24
INSTALLATION SUGGESTIONS
If your faxing application has difficulty locating the modem, check the fax
machine to be sure it is on and ready: Turn it off. Wait a few seconds. Turn it back
on.
Run the MS-DOS diagnostics to review the COM ports and IRQs for possible con-
flicts.
COMMUNICATION PORTS
The PC’s serial ports are usually configured as COM1 and COM2. They are
assigned Interrupt Request numbers (IRQs). IRQs establish priorities, which pre-
vent conflicts occurring when two devices want to use the same resources at the
same time.
To determine the availability of COM ports and their IRQs, Windows users can
run the MS-DOS diagnostics program. Change the directory to the root and type
msd
:
C:\WIN>
cd\
C:\>
msd
When the diagnostics menu appears, choose “COM Ports”. The next screen will
show what COM ports are enabled or available. Choose “IRQ Status” to show
what Interrupt Request status each COM port has. The COM ports must not have
the same IRQ: they are usually configured with IRQ4 and IRQ3.
For example :
The installation of an internal modem might cause an IRQ conflict between two
ports, even if no device is using the second port. The second port may have been
disabled to overcome the problem.
One solution is to remove the internal modem and re-enable the COM port.
Another solution is to install a third serial port.
‡
MS-DOS Version 5.0 and higher; Windows 95
IRQ STATUS
IRQ ADDRESS DESCRIPTION DETECTED HANDLED BY
IR3
IR4
F000: EF6F
CE29: 0096
COM2: COM4:
COM1: COM3:
COM2
COM1:
BIOS
BIOS